A variety of different types of debris known as "junk" can accumulate in a conventional oil well bore hole. Such "junk" includes metallic shavings, chips, twists, or curls dispersed throughout the length of the bore hole and which may adhere to the casing wall by natural magnetism. Such debris can also include portions of expendable tools, broken tools, or other tools items left in the well as well as any other foreign matter which may have fallen into the well. For example, when a portion of a casing is cut or milled in order to provide an offshoot from the bore hole, a considerable amount of cuttings are generated varying in length from several feet to several inches or less. It is roughly estimated that, in certain cases, for every five feet of casing milled approximately a barrel of cuttings are generated. In another situation, aluminum strapping bands are used to tie down electric cables in down hole electric pumps. These strapping bands can break and accumulate in the bore hole. The present invention is designed to primarily retrieve the type of junk described in the aforesaid two examples although it can also be used to retrieve other forms of conventional junk.
A number of conventional approaches exist for removing debris from the oil well bore hole such as the circulation of drilling mud to carry upwardly and outwardly from the well bore hole the smaller items of debris, the use of magnets to attract the metallic items and various other types of fishing equipment.
As a result of a patentability search conducted for the present invention, the following prior art patented approaches were uncovered:
______________________________________ INVENTOR U.S. PAT. NO. DATE ISSUED ______________________________________ Fortenberry 2,645,290 July 14, 1953 Baker 2,687,913 Aug. 31, 1954 Hall, Sr. 2,717,650 Sept. 13, 1955 Caudill 2,916,091 Dec. 8, 1959 Anderson 3,023,810 March 6, 1962 Jennings 3,382,925 May 14, 1968 Burba, Jr. 3,500,933 March 17, 1970 Baumstimler 3,651,867 March 28, 1972 Oliver 3,814,180 June 4, 1974 Best 4,189,000 Feb. 19, 1980 Wayt 4,332,296 June 1, 1982 ______________________________________
The 1970 patent to Burba, Jr. et al (U.S. Pat. No. 3,500,933 sets forth an apparatus for removing debris which includes a positive action wiper in the form of molded rubber cups for actually scraping the sides of the casing as the apparatus is moved downwardly into the oil well bore hole. As the Burba, Jr. et al apparatus is moved downwardly, the drilling mud is forced through the center of the tool and upwardly through an internal flow member, through a flapper valve and thence into an area of greater diameter which effectuates a separation of the heavier particles from the flow of the mud which are then caught in an entrapment chamber. As the tool is pulled upwardly, the flapper valve closes and the elongated slots on the side of the entrapment chamber allow the mud to flow freely therethrough while retaining the debris.
In the 1968 Jennings (U.S. Pat. No. 3,382,925), the 1974 Oliver (U.S. Pat. No. 3,814,180), and the 1962 Anderson (U.S. Pat. No. 3,023,810) patents, outwardly jetting fluid is utilized to dislodge debris accumulated on the walls of the casing. In these approaches, the outwardly jetting fluid provides the wiping action. The fluid is inputted from the drilling string and then is typically jetted outwardly around the periphery of the tool. In each of these approaches, a trap or chamber is provided for containing the collected debris. In the Anderson approach, a lower trap 25 is utilized to collect and contain the larger debris and a smaller trap 32 is utilized to entrap and contain the smaller debris. In these approaches the possibility exists that debris will be bypassed by the cleaning tool since the tool does not abut or actually scrape the sidewalls of the casing. In that event, debris can actually ball-up behind the tool and prevent removal of the tool from the bore hole.
The 1953 patent to Fortenberry (U.S. Pat. No. 2,645,290) also discloses a "junk" basket having a lower chamber for entrapping larger pieces of debris and an upper chamber for entrapping smaller pieces of debris. Fortenberry generates an upwardly directed high velocity jet for inducing a secondary circulation in the tool to cause the collected junk to move readily into the junk basket. Hence, Fortenberry is designed to be utilized while circulating the drilling fluid. As in the three above described patented approaches, Fortenbery also utilizes cutting teeth at the bottom of the tool in an effort to reduce the size of the larger pieces of debris to smaller pieces.
The 1954 patent to Baker (U.S. Pat. No. 2,687,913) also sets forth a tool for collecting and entrapping larger sized pieces of debris in a lower portion and smaller sized pieces of debris in an upper portion of the tool. Like the teachings of Burba, Jr. et al, Baker is designed to work in a static fluid environment (i.e., drilling fluid or other types of fluid are not pumped down into the tool to create various jets). As the tool is dropped, the Baker junk catcher is spring loaded so that when debris is encountered, the tool opens to collect the debris. When collected, the tool closes and can be lifted upwardly to remove debris.
The remaining patents uncovered in the search set forth various structural forms of well cleaning tools or casing scrapers embodying structural approaches which are not as close to the present invention as those disclosed in the above references.
Of all of the above prior patented art approaches, only the Baker and the Burba, Jr. patents, are relevant to the teachings of the applicant's invention by operating in a static fluid environment without the introduction of drilling fluid to create a jetting action. One disadvantage with the Burba, Jr. approach is the consumption of the wiper cups which, made of rubber, must be replaced after use. Furthermore, the wearing of the rubber cups causes rubber to be placed into the bore hole and rubber debris is difficult to retrieve. Additionally, Burba does not scrape or wipe at a point at or near the end of the tool and milled cuttings can ball up and nest between the rubber cup and the end of the tool possibly causing the tool to stick. And finally, Burba must permit junk to flow through a valve 80 before separation occurs. Such an arrangement may cause the clogging of the valve by large pieces of junk or by the capture of milled curlings. The disadvantage inherent in the Baker approach resides in the fact that actual wiping or scraping action against the casing wall does not occur. The possibility exists in Baker that debris clinging to the sides of the casing will be bypassed and, as previously discussed, ball up behind the tool.